Conduction through a SiO2 layer studied by electrochemical impedance analysis

This study addresses the effect of protons migrating from an aqueous solution on conduction through a dielectric SiO2 layer thermally synthesized on a highly n-doped silicon electrode (n(+)-Si). We investigate the conduction process, which involves an electrogenerated radical (hydrogen atom) in an n(+)-Si/SiO2/aqueous system, using electrochemical impedance analysis. With a sufficiently negative potential such as -2 V (vs. Ag/AgCI), the charge transfer resistance decreases as a function of time and no SiO2 layer breakdown is observed. A much thicker SiO2 layer exhibits similar behavior, which ensures negligible tunneling or leakage. Based on a Randles equivalent circuit involving a variable resistance, the impedance responses enable us to see what occurs in the SiO2 layer in this system. The results strongly imply that the faradaic reduction of protons occurs at the interface between n(+)-Si and SiO2. (C) 2017 Elsevier B.V. All rights reserved.